A jurisdiction is the place whose legal authority covers a matter. Gambling law is set locally. Whether a game is legal, who may offer it, the minimum age, and whether winnings are taxed all change from one country, state or region to the next. A game that is legal in one place can be banned in another. This site is country neutral and gives general information only, so readers should check the law and age limit that applies where they live before playing. Nothing here is legal advice.
Example
A form of betting may be licensed in one state and prohibited in the next state. A player's location, not the operator's, usually decides which rules apply.